“It provides a much more scenic and functional trails system, whether you’re riding a bike or taking a hike, or just out to do some bird-watching,” Cox said.

The park originally featured about 70 miles of meandering, informal dirt trails, he said. Some were forged by hikers and others by border patrol agents policing the area. The trails were poorly maintained, Cox said, and some strayed into habitat for the least Bell’s vireo, an endangered songbird.

To correct that, the county will realign the trails, using fencing to steer hikers, cyclists and equestrians away from sensitive areas. They’ll line the new trails with compacted, decomposed granite to provide a stable surface for visitors.

The $1.5 million grant from the Coastal Conservancy will cover about six and a half miles of new trails, plus some fencing and habitat restoration, including removal of invasive plants. The trails that will connect the western part of the Valley with Border Fields State Park, the Tijuana River National Estuarine Reserve, and potentially the California Coastal Trail, according to Assemblyman Ben Hueso, (D-San Diego) who helped secure the funding.

“They’ll be replaced with native vegetation, such as willows, that would have been a part of the natural flora of the Tijuana River hundreds of years ago,” Cox said.

Previous grants from the Coastal Conservancy and state Proposition 84 paid for about a mile of trails each, Cox said. The county also received $2.5 million in federal compensation for park acres lost to construction of the border fence, which paid for another seven miles of trails.

Officials with the conservation organization Wildcoast said the trail project will call attention to pollution problems in the river valley, and also highlight its assets.

“It will provide more access for the communities in San Ysidro and South San Diego and Imperial Beach, to the park,” said Wildcoast Executive Director Serge Dedina. “For some of those park poor communities in San Diego County, that’s a really important component of this.”